Paving process



May 9, 1939. F. s. FLECKENSTEIN PAVING PROCESS Filed Nov. 16, 1935 l/ea n'rzy Jurfaca Mariam of fine sin/2e and 750 WwEII bW I N V E N TO R F5 fiec/reizatez'ia ATTORNEY Patented May 9, 1939 5 UNITED STATES 2,157,330 PAVING rnocEss- Frederick S. Fleckenstein, Syracuse, N. Y., assignor to The Barrett Company, New York, N.'Y., a corporation of New Jersey i Application November 16, 1935, Serial No. 750,156

3 Claims. This invention relates to pavements and more particularly to pavements constituted of mineral aggregate and bituminous material.

It is an object-of this invention to provide a process of making bituminous pavements involving the application of a wearing course of mineral aggregate and a wearingsurface of bitumen coated aggregate which results in a dense and uniform wearing surface. Other objects and advantages of this invention will be apparent from the following detailed description thereof.

It has been common practice in the construction of bituminous pavements to apply to a suitable foundation bituminous concrete composed of graded mineral aggregate consisting of particles of crushed stone, gravelor slag, coated with bituminous cementand toroll this layer with a suitable road roller to form'the wearing course of the pavement.- A coating of bituminous cement, was applied to the wearing course and small stone particles spread over this coating in amount sufficient to fillthe surface voids. The small stone particles were rolled into the coating layer. Any loose material was swept off the road surface and then a second coating of bitu- 'minous cement was broom'ed over the surface.

This second coating was also covered with small stone particles. For the production of a satisfactory pavement it was found that atmospheric temperatures during the application of the wearing course should not be less than 45 F. and that traflic must be kept off the mad surface until the final covering material had been applied.

In accordance with this invention a wearing course of crushed stone, slag or other mineral -aggregate is applied in uncoated form to the road foundation and concurrently with the bonding together of the stone particles a wearing surface is formed thereon by applying thereto a mixture of finely divided mineral particles admixed with bituminous cement in amount such that the resultant mixture is sufiiciently fiuid under pressure to fiow into the voids of the stone layer to key with the stones of the wearing course and with circular openings of 1 inch diameter is employed for the wearing course. This stone without further treatment is applied to the road foundation and rolled by means of a usual r ijad Troller to the desired contour of the road cu The wearing surface is next applied. Thema terial of the wearing surface is made byrnixing finely divided mineral particles, such as sand, gravel or crushed slag, with a bituminous binder, preferably coal tar, which, may be a straight dis: tilled tar or a cut-back tar, i. e., atar made by mixing a pitch remainingfrom the distillation of tar with a distillate oil. Eithera straight distilled tar having a specific viscosity Engler at 40 C. of from 25 to or a cut,back tar having a specific viscosity Engler at 40 C.'of from 40 to,60, maybe employed.

The finely divided mineral particles shouldbe in a stateof sub-division comparable to-that of sand. One. example of mesh characteristic of the finely dividedaggregate found s'uitableforthe wearing surface is as follows;

Percent Passing A" screen to Passing a No. 10 sieve 50t0 95 Passing a No. 200 sieve 0 to 15 be above F., preferably at a temperature of from 60 F. to 100 F. The tar should be at a temperature .of from 80"v F. to 150 F. A straight run tar at a temperature of about F. may be mixed with the finely divided stone. If a cut- ,back tar is used it is preferably heated to a somewhat lower temperature.

The amount of tar added to produce the fine mix is preferably from 8 to 10 per cent by weight of the complete mixture, i. e., the final mixture is constituted of from 90 to 92 per cent bitumen and 8 to 10per cent tar. This fine mix may be readily spread over the layer of uncoated stone at atmospheric temperatures to form a wearing surface, 1. e. the process herein described is a cold-lay process. The fine mix, after application, is well rolled. It has sufiicient fluidity under pressure to flow into the interstices of the underlying stone layer to key with the stones of the course and cement them together. Enough tar is present in the fine mix so that under pressure a certain amount is squeezed out of the mix and coats some of the stone of the course on which the mix is laid, thus aiding the bonding of the fine mix with the underlying course. Under rolling pressure the fine mix sets to form a dense wearing surface bonded with the underlying wearing course.

It will be noted that in the practice of this invention in order to produce an emcient pavement it is necessary to apply stone only to the road foundation and then apply a wearing surface of the fine mix, which upon rolling not only provides an efficient wearing surface-but also functions J70 key or bond the wearing surface with the wearing Since certain changes may be made in carrying out the above process without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in. a limiting sense.

I claim:

1. A cold-lay process of building a road pavement which comprises applying a layer of clean,

coarse aggregate unc oated with bitumen or a bitumen solvent to a foundation tov form a wearing course, rolling the wearing course to compact the same and then applying thereover alayer of aggregate particles in a state of subdivisionsimilar to that of sand, admixed with coal tar of a specific viscosity Engler at, 40 C. of from 25 to 65 in amount such that the resultant mixture is suificiently fluid under pressure to flow into the voids of the underlying. coarse aggregate layer, and rolling the second mentioned layer to cause it to firmly bond with the underlying layer to bond the particles of the underlying layer to each other, the fine aggregate and coal tar constituting the wearing surface and binder of the pavement.

2. A cold-lay pavement building process which comprises applying a layer of clean, coarse aggregate particles uncoated with bitumen or a bitumen solvent to form a wearing course, spreading over this layer a bituminous mixture constituted of finely divided aggregate particles having the following mesh characteristics:

Percent Passing a screen 90 to 100 Passing a No. 10 sieve 50 to 95 Passing a No. 200 sieve to 15 fine aggregate and tar constituting the wearing surface and binder of the pavement.

3. A cold-lay pavement building process which comprises applying a layer of clean, coarse graded aggregate particles of a size such that the particles pass through a screen with circular openings of 3 inch diameter and are retained on I a screen with circular openings of 1 inch diameter to form a wearing course, said aggregate being uncoated with bitumen or a bitumen solvent, spreading over this layer a bituminous mixture constituted of finely divided aggregate particles having the following mesh characteristics:

. Percent Passing a A" screen" 90 to 100 Passing a No. 10 sieve 50 to 95 Passing a No. 200 sieve 0 to admixed with tar having-a specific viscosity Engler at 40 C. of from to 65, in the proportions of from 8 to 10 per cent. tar and 90 to 92 per cent.

- finely divided aggregate and compressing the said mixture to cause it to fiow into the interstices of the underlying coarse aggregate course to key therewith and cement the stones together, the fine aggregate and tar constituting the wearing surface and binder of the pavement.

FREDERICK S. FLECKENS'I'EIN. 

